why x-t correlation may be important for hbt
DESCRIPTION
Why x-t correlation may be important for HBT Origin of a large&positive x-t correlation: partonic? resonance decays? hadronic rescatterings? Can a (hydro-type) negative x-t correlation survive decays/rescatterings in a transport model? Rout/Rside: - PowerPoint PPT PresentationTRANSCRIPT
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
● Why x-t correlation may be important for HBT● Origin of a large&positive x-t correlation:
partonic? resonance decays? hadronic rescatterings?
● Can a (hydro-type) negative x-t correlation
survive decays/rescatterings in a transport model?
• Rout/Rside: from Gaussian fit vs from emission function
Strong and positive x-t correlation and its effect on Rout/Rside
Zi-Wei LinThe Ohio State University
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
HBT Radii fromEmission function S(x,p) or correlation function C(q)
If source is Gaussian in space-time, then:
Rsource,ij=Rfit,ij
1) Curvature at q=0: 2) Often use 4-parameter fitfor C(q) w/o Coulomb effects:
Pratt,PRL84
Pratt,PRL84Wiedemann,PRC57
Dx,y=<x*y>-<x><y>
. 2
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
Study HBT with a transport model
Advantage:freezeout in transport is natural as the mean free path grows too big compared with system size
How to relate to hydro calculations (Cooper-Frye formula at a sharp hypersurface is usually imposed)
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
HIJINGenergy in strings and minijet partons
ZPC (Zhang's Parton Cascade)
Till Parton freezeout
ART (A Relativistic Transport model for hadrons)
A+A
Decay all resonances;Final particle spectra
Structure of AMPT modelwith String Melting
Fragment excited strings into partons
Coalescence into hadrons
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
ZWL,Ko&Pal,PRL89
From Gaussian fits to 3-d correlation function C(q)
Au+Au at 130AGeV(b=0 fm)
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
Why x-t correlation may be important?
Spatial-size x-t correlation duration-time
Magnitude and sign of x-t correlationare important for Rout, Rout/Rside, & extraction of duration-time
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
Correlations in pion emission source: out-side out-t
<Xout (t)>
Positive and large, tends to reduce Rout Values: (17fm)**2 = 185 -2*168 + 431
SourceSpatial-size x-t correlation Duration time
ZWL,Ko&Pal,PRL89
Note:includes decays
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
out-side out-t
K emission source (excludes decays):
ZWL&Ko,JPG29
Values: (3.4fm)**2 = 35 -2*22 + 20
K source
<Xout (t)>
also positive and large for K
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
●Turn off decays to study HBT radiifrom the emission function
●Test hydro-like negative x-t correlationupon hadron formation in AMPT
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
Pions at freezeout
xout
xsid
e
x
y
mostly partons
~surface emission ~volume emission
<xout> >0parton transverse flow
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
x-t correlation for pions
Au+Au at 200AGeV (b=0 fm)
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
Already present for quarksx-t correlation for pions
Au+Au at 200AGeV (b=0 fm)
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
Effect of decays on source radii
Hadronic decays produce mt-dependence in Rout & Rside
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
Rout/Rside from emission function
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
Can an initial negative x-t correlation survive later?
Test negative x-t correlation from hydro models at RHIC energies
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
large initial Rout/Rside ratio (source)
Initial hadrons:
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
large final Rout/Rside ratio (source)
Negative x-t term becomes positive after hadronic scatterings
Final hadrons:
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
Hardtke&Voloshin, PRC61
Radii are different from source or from Gaussian fit to C(Q)
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
from source from C(Q) fit
big decrease for fitted Rout, Rout/Rside
AMPT: Au+Au at 200AGeV at b=0 fm, 3mb
Rout/Rside=1
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
from source from C(Q) fit
With an initial negative x-t correlationat hadron formation
huge decrease for fitted Rout & Rout/Rside Rout/Rside >>1 ~=1
Rout/Rside=1
Zi-Wei LinZi-Wei Lin Collective flow and QGP propertiesCollective flow and QGP properties 11/19/200311/19/2003
●Strong and positive xout-t correlation term ●tends to reduce Rout and Rout/Rside.●already present at parton freezeout/hadron formation●An initial negative x-t correlation can lead to
large Rout/Rside (when evaluated from emission function)
●Rout/Rside: >1 from emission function
~=1 from Gaussian fits to C(Q).
●Even with an large initial negative x-t
(with Rout/Rside >>1 from the emission function)
●Further investigation is needed to find the reason.
HBT summary